Label printing techniques: starting from the usage environment

Before asking "what printing technology should we use?" or "paper or film?", the question Sinh Vũ always asks first is: where will this label live? In the freezer, in the sun, on a shampoo bottle, or on a shipping box? The actual usage environment determines the surface material and type of adhesive. Printing technology comes later, once those two factors are clear.

Surface materials: the foundation of all labels.

Pressure-sensitive labels (stickers that can be peeled and applied without additional glue) consist of three layers: the printable surface layer, the adhesive layer, and the release liner. The surface layer is what you see and touch, so it must be suitable for the conditions the label will encounter.

• Paper: suitable for dry labels, under normal conditions. Low cost, easy to print in color, but absorbs moisture, smudges easily, and can peel when exposed to water or oil.
• BOPP film (Biaxially Oriented Polypropylene): one of the popular label materials due to its durability, moisture resistance, and reasonable cost. It works well for bottles that come into contact with water, oil, or light friction.
• PET film (Polyethylene Terephthalate): stiffer than BOPP, better heat and solvent resistance, suitable for harsher environments.
• Brittle materials or those that destroy structure when peeled: Used for warranty labels or anti-counterfeiting labels, leaving clear traces when someone attempts to peel them off.

Keo: factors often overlooked

Good surface materials with the wrong adhesive will still peel off. The adhesive needs to match both the environmental conditions and the surface being adhered to.

• High-bond permanent adhesive: for surfaces that are hard to bond or require long-lasting adhesion, which cannot be removed.
• Removable adhesive: used when labels need to be removed without leaving adhesive residue.
• Low-energy plastic adhesive: some plastics like PP and HDPE have surfaces that are difficult to bond. Regular adhesives may not hold, requiring specialized adhesives for these surfaces.
• Cold or freeze-resistant adhesive: for labels used in refrigerators or freezers, as adhesives typically lose their bonding strength at low temperatures.

Printing technology: scale determines the choice

After selecting materials and adhesives, the printing technology depends on the quantity and stability of the samples.

• Flexo (flexographic printing): printing using flexible plates, suitable for large runs with stable designs. The initial plate-making cost is higher, but the price per label is lower when the quantity is large enough. Commonly used in industrial roll label production.
• Digital printing: No printing plates are needed, and data can be changed with each print. Suitable for small runs, many different SKUs, or labels with variable information such as batch numbers, production dates, or unique barcodes.

No technology is absolutely better. The mistake is choosing technology that does not match the actual scale, leading to higher unit costs than necessary.

Specialized labels: specific requirements for each industry.

Some types of labels have requirements that go beyond standard aesthetics and adhesion.

• Chemical warning labels: must comply with the Globally Harmonized System (GHS), including mandatory information content and standardized warning symbols. Materials and inks need to withstand the environmental conditions that the chemicals will encounter.
• Marine transport label: BSI's BS5609 standard checks labels against multiple criteria, including criterion 3, which tests the print for durability, abrasion resistance, and legibility after prolonged immersion in seawater. The label structure must meet the requirements for the substrate, adhesive, and ink.
• Freezer or outdoor labels: require adhesives that can withstand low temperatures or ultraviolet rays, along with a protective coating on the printed surface.

A label is not just a printed surface. It is a system consisting of the surface, adhesive, and finishing, which must function correctly under real-world conditions throughout the product's lifecycle.

Practical experience, Sinh Vũ Studio

Common mistakes and how to avoid them

• Using paper labels for bottles that come into contact with water or oil: the labels smudge and peel after a short time.
• Choose adhesive that is not suitable for low-energy plastic surfaces: labels do not stick or peel off even though the surface material is correct.
• Ignore the protective lamination layer for labels that endure friction: printed surfaces scratch quickly, losing information and aesthetics.
• Creating chemical labels without referencing GHS: missing mandatory information or fading ink when exposed to chemicals, which can pose legal risks.
• Die-cut file not matching the printing house's specifications: misaligned cut lines, insufficient safety area, unusable labels.

Sinh Vũ creates the cutting template files according to the printing partner's machine specifications, aligning the cutting borders and safe zones before sending them for production. Printing costs and minimum quantities are reported directly by the printer as they depend on equipment and materials for each batch, which is not something Sinh Vũ commits to.